Problems

  1. English Units - Construct an HEC-RAS model using the data in the following tables and answer the questions that follow. The channel discharge is 1200 ft3/s along its entire length, the flow regime is subcritical, and the water surface elevation at river station 1.0 is 163.5 ft mean sea level. Note that the left and right bank stations of the main channel are indicated by the shaded boxes.
    1. What is the computed water surface elevation at river station 2.0?
    2. What is the average velocity in the main channel at river station 3.0?
    3. What is the head loss due to friction between sections 1.0 and 2.0?
    4. What are the conveyances for the left overbank, main channel, and right overbank at river station 4.0?
    5. What is the energy grade elevation at river station 2.0?
    6. What is the energy correction factor (a) at river station 3.0?

      7. River Station
      Left Overbank
      Main Channel
      Right Overbank
      Manning's n
      Length, ft
      Manning's n
      Length, ft
      Manning's n
      Length, ft
      1.0
      0.035
      N/A
      0.02
      N/A
      0.04
      N/A
      2.0
      0.035
      250
      0.02
      250
      0.04
      250
      3.0
      0.035
      330
      0.02
      340
      0.04
      350
      4.0
      0.035
      500
      0.02
      500
      0.04
      500

      River Station 1.0
      River Station 2.0
      River Station 3.0
      River Station 4.0
      Station, ft
      Elevation, ft
      Station, ft
      Elevation, ft
      Station, ft
      Elevation, ft
      Station, ft
      Elevation, ft
      200.0
      165.0
      200.0
      165.4
      200.0
      165.8
      189.9
      167.3
      206.1
      163.3
      206.1
      163.6
      206.1
      164.1
      216.7
      164.4
      220.9
      161.0
      235.2
      163.4
      220.9
      161.8
      220.9
      162.2
      237.8
      160.6
      237.8
      161.0
      251.9
      161.4
      237.8
      161.8
      250.0
      158.0
      250.0
      158.4
      254.6
      160.2
      250.0
      159.2
      267.9
      158.8
      269.1
      158.2
      266.9
      158.7
      267.9
      159.5
      278.1
      158.5
      278.3
      157.7
      278.3
      158.5
      278.3
      159.4
      290.0
      158.0
      290.0
      158.5
      290.0
      158.8
      290.0
      159.2
      298.9
      161.0
      298.9
      161.4
      298.9
      161.8
      298.9
      162.2
      305.7
      163.3
      314.2
      162.1
      316.1
      162.7
      320.3
      164.1
      310.0
      165.0
      319.8
      166.4
      334.8
      164.9
      332.4
      167.3

      SI Units - Construct an HEC-RAS model using the data in the following tables and answer the questions that follow. The channel discharge is 34 m3/s along its entire length, the flow regime is subcritical, and the water surface elevation at river station 1.0 is 49.8 m mean sea level. Note that the left and right bank stations of main channel are contained in the shaded boxes. Answer questions (a) through (f) above.

      River Station
      Left Overbank
      Main Channel
      Right Overbank
      Manning's n
      Length, m
      Manning's n
      Length, m
      Manning's n
      Length, m
      1.0
      0.035
      N/A
      0.02
      N/A
      0.04
      N/A
      2.0
      0.035
      76.2
      0.02
      76.2
      0.04
      76.2
      3.0
      0.035
      100.6
      0.02
      103.6
      0.04
      106.7
      4.0
      0.035
      152.4
      0.02
      152.4
      0.04
      152.4

      River Station 1.0
      River Station 2.0
      River Station 3.0
      River Station 4.0
      Station, m
      Elevation, m
      Station, m
      Elevation, m
      Station, m
      Elevation, m
      Station, m
      Elevation, m
      61.0
      50.3
      61.0
      50.4
      61.0
      50.5
      57.9
      51.0
      62.8
      49.8
      62.8
      49.9
      62.8
      50.0
      66.1
      50.1
      67.3
      49.1
      71.7
      49.8
      67.3
      49.3
      67.3
      49.4
      72.5
      49.0
      72.5
      49.1
      76.8
      49.2
      72.5
      49.3
      76.2
      48.2
      76.2
      48.3
      77.6
      48.8
      76.2
      48.5
      81.7
      48.4
      82.0
      48.2
      81.4
      48.4
      81.7
      48.6
      84.8
      48.3
      84.8
      48.1
      84.8
      48.3
      84.8
      48.6
      88.4
      48.2
      88.4
      48.3
      88.4
      48.4
      88.4
      48.5
      91.1
      49.1
      91.1
      49.2
      91.1
      49.3
      91.1
      49.4
      93.2
      49.8
      95.8
      49.4
      96.3
      49.6
      97.6
      50.0
      94.5
      50.3
      97.5
      50.7
      102.0
      50.3
      101.3
      51.0

  2. English Units - Construct an HEC-RAS model for the system shown in the figure, and answer the questions that follow. The channel is trapezoidal with a bottom width of 49.2 ft and 3:1 side slopes. The channel slope is 0.002, the material is concrete (Manning's n = 0.013), and the length is 492.1 ft. A flow of 11,300 ft3/s enters the channel from the broad-crested weir, as illustrated in the figure.

    3. Click here for larger image

    1. Is the flow in the channel subcritical or supercritical?
    2. What is the depth of water at the upstream end of the channel?
    3. What is the depth of water at the downstream end of the channel?
    4. What should be the minimum depth of the channel?
    5. Does uniform flow occur within the channel?
    6. What type of flow regime does this profile depict?

      7. SI Units - Construct an HEC-RAS model for the system shown in the figure, and answer the questions that follow. The channel is trapezoidal with a bottom width of 15 m and 3:1 side slopes. The channel slope is 0.002, the material is concrete (Manning's n = 0.013), and the length is 150 m. A flow of 320 m3/s enters the channel from a broad-crested weir, as illustrated in the figure. Answer questions (a) through (f) above.

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